1. Field of the Invention
The present invention relates to an object lens drive unit for driving an object lens in an optical disc drive for focusing write/read light on a recording surface of an optical disc.
2. Background Art
Optical disc drives for writing or reading information on optical recording medium discs are capable of recording relatively large volumes of information on such discs. The disc media have large stiffness and are easy to handle. For these reasons, optical disc drives are widely used as an external recording unit for computers or as a device for recording video and audio data. In such optical disc drives, an object lens drive unit is used for driving an object lens, with which the write/read light is focused on the recording surface of an optical disc, in a focusing direction (in which the lens is moved toward or away from the optical disc surface), in a tracking direction (radial direction of the optical disc), in a radial tilt direction (in which the lens is tilted in the radial direction of the optical disc), and in a tangential tilt direction (in which the lens is tilted in a tangential direction to the optical disc). Patent Document 1, for example, discloses such object lens drive unit in a conventional optical disc drive.
As shown in FIG. 1 of Patent Document 1, for example, the conventional object lens drive unit is composed of a moving part including an object lens, support members for supporting the moving part, and a magnetic circuit consisting of a yoke and permanent magnets. The moving part is fitted with a focusing coil and a tracking coil. As a drive current flows through the focusing coil, it interacts with the magnetic flux from the permanent magnets, thereby generating an electromagnetic force. The electromagnetic force drives the moving part in the focusing direction. Similarly, as a drive current flows through the tracking coil, it interacts with the magnetic flux from the permanent magnets, thereby generating an electromagnetic force, with which the moving part is driven in the tracking direction. The moving part is also fitted with a radial tilt coil or a tangential tilt coil. As a drive current flows through the radial tilt coil, it interacts with the magnetic flux from the permanent magnets, thereby generating an electromagnetic force with which the moving part is driven in the radial tilt direction. Similarly, as a drive current flows through the tangential tilt coil, the current interacts with the magnetic flux from the permanent magnet, thereby generating an electromagnetic force with which the moving part is driven in the tangential tilt direction.
In this object lens drive unit, a plurality of support members, which are made of metal cores or the like, are disposed such that they form parallel links. One ends of the support members are fixed to the disposed moving part and the other ends thereof are fixed to a fixing portion. Further, a deformable substrate or the like is interposed on the fixing-portion side of the support members so as to reduce the stiffness of the support members in the axial direction thereof, so that the object lens can be driven in the tangential tilt direction.
Patent Document 1: JP Patent Publication (Kokai) No. 2004-95133 A (pp. 14-25, and FIG. 1)